Electrophotographic reproduction system utilizing ion modulator and dielectric and dielectric imaging surface

ABSTRACT

An electrophotographic system is described in which a photoconductive ion modulator screen is used in conjunction with an anodized aluminum dielectric imaging surface. This combination enables the steps of image transfer and fixing to be carried out simultaneously without destroying the latent image produced on the dielectric imaging surface.

United States Patent Sable Sept. 23, 1975 ELECTROPHOTOGRAPHIC REPRODUCTION SYSTEM UTILIZING ION MODULATOR AND DIELECTRIC AND DIELECTRIC IMAGING SURFACE Harvey J. Sable, Cleveland, Ohio Addressograph Multigraph Corporation, Cleveland, Ohio Filed: Mar. 27, 1974 Appl. No.: 455,206

Inventor:

Assignee:

US. Cl. 96/l.4; 355/3 R Int. Cl. GOBG 13/14; 0036 5/04 Field of Search ..96/1.5, 1.4; 355/3 R;

References Cited UNlTED STATES PATENTS 5/1974 Blake 96/l.4

FOREIGN PATENTS OR APPLICATIONS 575.070 4/1959 Canada 96/].5 763.900 7/1967 Canada 96/].5

Primary E.\'am1'nerNorman Gv Torchin Assistant Examiner-John L. Goodrow Attorney. Agent. or Firm-Michael A. Kondzella [57] ABSTRACT 11 Claims, 3 Drawing Figures US Patent Sept. 23,1975 3,907,560

H/G/l VOL TAGE ELECTROPHOTOGRAPHIC REPRODUCTION SYSTEM UTILIZING ION MODULATOR AND DIELECTRIC AND DIELECTRIC IMAGING SURFACE BACKGROUND OF THE INVENTION This invention relates to electrophotographic reproduction systems and in particular to an electrophotographic process and device in which an image is transferred from a suitable dielectric surface to a receiving surface such as plain paper.

Electrophotographic processes are well known with many ramifications having been described since the earliest disclosure thereof by Chester F. Carlson in US. Pat. No. 2,297,691. In that patent a photoconductive insulating material such as sulfur, anthracene, anthraquinone or selenium was utilized as the imaging surface. Since then various other types of photoconductors have been disclosed. inorganic crystalline photoconductive compounds such as zinc oxide, used in an insulating organic resin binder, were disclosed in US. Pat. No. 3,121,006 to Arthur E. Middleton and Donald C. Reynolds. Various organic photoconductors have also been described as imaging surfaces. Polyvinylcarbazole is described as a photoconductor in US. Pat. No. 3,037,861 to H. Hoegl, O. Sus and W. Neugebauer. Other organic photoconductors which are known for this purpose include the polyvinylbenzocarbazoles disclosed in US. Pat. No. 3,751,246 to Helen C. Printy and Evan S. Baltazzi and the polyiodobenzocarbazoles described in US. Pat. No. 3,764,316 to Earl E. Dailey, Jerry M. Barton, Ralph L. Minnis and Evan S. Baltazzi, both assigned to the same assignee as this invention.

Other classes of organic photoconductors are the benzofluorenes and dibenzofluorenes described in US. Pat. No. 3,614,412 to William .I. Hessel and the cumulenes described in US. Pat. No. 3,674,473 to Robert G. Blanchette also assigned to the same assignee as this invention.

The organic photoconductors are generally utilized in conjunction with a suitable sensitizer to extend the spectral range of the photoconductor. Dyes may be used for this purpose. Another class of materials which are widely used are the pi acids. Representative of these compounds are the oxazolone and butenolide derivatives of fluorenone, described in US. Pat. No. 3,556,785 to Evan S. Baltazzi, the dicyanomethylene substituted fluorenes, described in US Pat. No. 3,752,668 to Evan S. Baltazzi and the bianthrones de scribed in US. Pat. No. 3,615,411 to William .1. Hessel, all assigned to the same assignee as this invention.

Prior art electrophotographie processes in general consisted of uniformly charging a photoconductor electrostatically in the dark, exposing the uniformly charged photoconductor to a pattern of light and shadow corresponding to the image to be reproduced, whereby the photoconductor was selectively discharged in the light-struck areas, contacting the resulting latent electrostatic image with a contrasting colored dielectric powdered material known as a toner to develop the image and either permanently fixing the toned image to the photoconductive surface or transferring it to a suitable receiving material such as a sheet of paper and thereafter permanently fixing the visible image to such receiving material.

Recently use has been made of ion modulators comprising a conductive grid or screen upon which is deposited a layer of photoconductor. The ion screen modulator is first uniformly charged and then exposed to an image of the original to be reproduced so as to produce a latent electrostatic image thereupon. A stream of ions impinged upon the screen is modulated by the latent electrostatic image thereon so that a latent electrostatic image comparable to that on the screen is formed upon a dielectric imaging surface placed in the path ofthe ion stream. The resulting latent electrostatic image is then developed upon the imaging surface. transferred to a sheet of paper or other receiving material and then permanently fixed thereto. The use of such screens is described. for example, in US. Pat. No. 3,220,324 to Christopher Snelling.

The various prior art processes disclosed above have certain disadvantages. For example. where it is necessary to transfer a toned image from a photoconductive surface to a receiving material, such as a sheet of plain paper, it is necessary to use a corona discharge in order to accomplish the transfer. First, the corona discharge required for transfer destroys the usefulness of the latent image which must therefore be reformed for each copy. Second, the transferred image must be fixed following transfer, usually by means of heat or pressure. These shortcomings add process steps which put an upper limit on copying speed. Where the image is fixed upon the photoconductive surface itself, it is also necessary to use as the photoconductive surface a costly, specially formulated material such as zinc oxide coated paper rather than plain paper.

OBJECTS It is a principal object of this invention to provide an electrophotographic reproduction system in which transfer of a toned image to a receiving material and fixing of the image are accomplished simultaneously.

Another object of this invention is to provide an electrophotographic duplicating system which is capable of producing a number of copies without re-imaging the original after production of the first and successive copies.

Another object of this invention is to provide a system for electrophotographic copying which is equipped with a dielectric surface which is hard and resistant to wear and which can be used for pressure fixing of a toned image.

Other objects and advantages of this invention will become apparent from the following detailed disclosure and description.

SUMMARY OF THE INVENTION It has been found that the combination of a photoconductive ion modulator and an anodized aluminum dielectric imaging surface can be used to achieve the above noted objects. Use of this combination results in a system which is capable of simultaneous transfer of a toned image from the dielectric imaging surface to plain paper and pressure fixing of the image thereon. Since the latent electrostatic image persists upon the dielectric surface after transfer it is unnecessary to reimage the original or reproduce the latent electrostatic image upon the dielectric surface from the ion screen modulator between successive copies which can be made by merely toning the dielectric surface each time a copy is desired.

Use of the system of this invention results in a simpler and faster process. Since the latent electrostatic image on the ion screen modulator can be reproduced on a dielectric surface without destroying its usefulness. it does not have to he created anew for each copy of the same original. In addition, the dielectric surface upon which a second latent image is reproduced is more durable and wear resistant than the photoconductive screen itself. This durability permits the use of sufficient pressure to achieve simultaneous transfer and fixing of the toned image. Since corona discharge is not used in transferring the image. the integrity of the latent electrostatic image upon the anodized aluminum dielectric surface is retained and the image can be retoned, transferred and fixed many times without reimaging.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is'a diagrammatic view of an apparatus embodying the general features of this invention.

FIG. 2 is a diagrammatic view of a specific embodiment of this invention.

FIG. 3 is a diagrammatic cross-sectional view of an anodized aluminum surface such as used in this invention.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIG. 1 an imaging unit to be described hereinafter in greater detail is positioned adja cent a drum 11. Downstream of imaging unit 10 adjacent to the drum 11 is positioned developing unit 12. Receiving material 13 is fed from supply roll 14 between drum 11 and pressure roll 15.

Imaging unit 10 functions to provide a latent electrostatic image upon the surface of drum 11 corresponding to an original which is to be reproduced. Drum 11 is rotated so that the resultant latent electrostatic image is advanced to developing unit 12 for development of the latent electrostatic image. Developing unit 12 may be any conventional type of developing device such as a cascade, powder cloud or magnetic brush developing device. The resulting developed image is then transferred from drum [1 to receiving material 13, which may be, for example, plain paper, by passing receiving material 13 between the surfaces of drum 11 and pressure roll 15. Simultaneous transfer and fixing of the developed image is achieved in this step since pressure roll 15 exerts sufficient pressure against the surface of drum 11 to both transfer the developed image from the surface of drum 1! to receiving material 13 and fix the image thereon.

In FIG. 2 a specific embodiment of this invention is shown illustrating in some detail the various components used therein. In this embodiment imaging unit 10 includes ion modulator screen which comprises a conductive screen and a coating thereon of a photoconductor. Screen 20 has imparted to it a uniform electrostatic charge in the dark by means of corona electrode 21 provided with high voltage source 22 and grounded shield 23. After the charging of the photoconductive layer of the ion modulator screen 20 has been completed, the corona is shut off and original 24 to be reproduced is illuminated by means of lamps 25 whereby a pattern of light and shadow corresponding to original 24 is focused upon ion modulator screen 20 by means of lens 26 resulting in selectively discharging those areas of the ion modulator screen corresponding to the light areas in the original. Corona electrode 21 is tlien'turned on again. drum II is rotated and an ion stream is caused to impinge upon ion modulator screen 20 resulting in the passage through the screen and mask 27 of ions in a pattern corresponding to the original 24 and the formation of a latent electrostatic image upon the anodized aluminum dielectric surface of drum II. Corona electrode 2] is then turned off and as drum 11 rotates the surface which carries the latent electrostatic image is moved into position adjacent developing unit 12 which includes magnetic brush 28. Toner particles 29 are supplied by means of magnetic brush 28 and caused to adhere to the dielectric surface of drum 1] in a pattern corresponding to the original 24. As drum 11 continues to rotate the toned image held upon its surface by electrostatic charges is compressed between pressure roll 15 and drum l1 and transferred to receiving material 13, most suitably plain paper. which is fed from supply roll 14 to the nip between drum 11 and pressure roll 15. Contact between drum 11 and pressure roll 15 is made under pressure so that the toner carried by drum 11 in the form of a toned image is simultaneously transferred to receiving material 13 and permanently fixed thereon. as depicted at 30.

Due to the rotation of drum 11 beneath mask 27 the area subjected to imaging at any given time is made to approximate a flat surface.

If the machine described above is to be used for pro ducing a single copy, the latent electrostatic image which is retained upon drum 11 following transfer and fixing can be easily removed by exposure to a stream of high humidity air as shown at 31 or by discharging with a suitable A.C. corona, not shown.

Where, however, more thanone copy is desired the latent electrostatic image remaining upon the anodized aluminum surface of drum 11 following transfer of the toned image to receiving material 13 is rotated past imaging unit 10, which is shut off, to magnetic brush 28 for retoning and then to pressure roll 15 for transfer and fixing of the developed image as before. The foregoing cycle is repeated as many times as dcsired depending upon the numbcr of copies which are to be made. Since the anodized aluminum surface of drum 11 is capable of retaining the latent electrostatic image for an extended period of time it is possible to make a large number of copies by this method. In this mode the machine functions as an electrostatic duplicator. Following the last transfer; that is, the production of the last copy desired in a given run, the latent electrostatic image remaining upon the anodized aluminum surface of drum 11 is removed as described above and the surface of drum 1] is ready for re-imaging to reproduce a different original.

As shown in FIG. 3 the surface of drum 1] consists of anodized aluminum layer 40 deposited upon aluminum substrate 41. The anodized aluminum surface is of the type characterized as barrier type aluminum oxide since the porous type of aluminum oxide functions as a conductor rather than a dielectric as desired here.

This type barrier aluminum oxide is readily formed upon an aluminum surface by subjecting aluminum to an electrolytic oxidation using a bath comprised of a buffered acidic electrolyte. In providing a barrier type layer the pH of the electrolyte should be buffered in the range of about from pH 6 to pH9. Electrolytes in the range of from about pH 7 to pH v9 are preferred since utilization of such electrolytes results in formation of a relatively pure barrier layer film. Acids which may be used as electrolytes include such weak acids as citric acid, malic acid, glycolic acid and boric acid. ln the case of boric acid baths an aqueous solution of a mixture of boric acid and borax can be used to provide the requisite buffered elcctrolytel Such electrolyte can also include materials such as ethylene glycol which improve the electrolytic deposition of the barrieraluminum oxide. The potential of the electrolytic cell in which the deposition of aluminum oxide upon the aluminum substrate occurs should be controlled within the range of about from l00 volts to 700 volts. A voltage in the range of from about 200 volts to 400 volts is preferred. Using baths of the type disclosed above and potentials as above indicated a thickness of about from 5,000 angstroms to 10,000 angstroms can be obtained in a reasonable period of time. A convenient rule of thumb is that a deposition of about 14 angstroms per volt is obtained utilizing the electrolytes described above.

Plating temperatures in the room temperature range are preferred with satisfactory results being obtained using temperatures in the range of about from C to C. The time necessary to provide aluminum oxide barrier type layers of the desired composition can vary from a few minutes to several hours. In general, it is found that about from minutes to 2 hours is a range which provides satisfactory results. The utilization of diols or triols in the acid electrolytic baths is believed to facilitate the electrolytic oxidation by increasing the acidity of the bath without increasing the solvency of the bath for aluminum or aluminum oxide. Presumably, some sort of complex formation involving the acid and diol or triol is involved.

In order to achieve the results of simultaneous transferring and fixing of the toned image in this invention, it is necessary that a minimum pressure be exerted upon the receiving material which is passed between the anodized aluminum dielectric imaging surface and the pressure roll. lt has been found that pressures in the range of about from 200 to 300 pounds per linear inch are effective for this purpose. These pressures can be achieved using a pressure roll of the type commonly used in pressure fixing in electrostatic copying machines. One type of such roll is a nylon covered steel roll which has the advantage over a plain steel roll that it is somewhat resilient.

For the pressure fixing of toned images it is desirable to use a toner in the developing system which is particularly adaptable to pressure fixing. A variety of toners of this kind are well known such as those described in U.S. Pat. No. 3,764,538 to Loren E. Shelffo and U.S. Pat. No. 3,775,326 to Virgil W. Westdale both assigned to the same assignee as this invention. It should be understood, of course, that various other toners are likewise useable in carrying out the process of this invention.

This invention will be better understood by reference to the following examples which are given for the purpose of illustration and are not intended to unduly limit the invention herein which is defined in the claims appended hereto.

EXAMPLE 1 Boric Acid (H grants Sodium Tetraborate (Borax) 5.6 grams Na B,0 5 H 0 Deionizcd water 1 liter The bath was maintained at a temperature of 20C.

The aluminum sample was connected to the positive terminal ofa 0 volt D.C, power source. The negative terminal was connected to a 4 5/16 inch O.D. X A; inch thick graphite plate suspended in the bath parallel to the aluminum anode with approximately one inch separating the anode from the cathode. The voltage was then raised to the maximum. The initial current was seen to drop rapidly from 7-8 amperes to nearly 0 in approximately 10 minutes. A higher voltage supply giving 0 400 volts DC. at a maximum of ma. was then connected to the cell with the same polarities and the voltage was adjusted to maintain the limit of current of the power supply. After about 30 to 40 minutes the maximum supply voltage was attained at a current flow of approximately 10-20 ma. The sample was then removed from the bath, washed in tap water and oven dried at 80C for 20 minutes. The thickness of the anodized aluminum layer was about 5,600 angstroms.

A latent image was projected onto the anodized aluminum surface of the aluminum sample by passing ions from a corona wire connected to the negative terminal of a 6,000 volt DC. power supply through a 200 mesh stainless steel screen onto the anodized aluminum surface. The screen was connected to the negative terminal of a 15,000 volt DC. power supply and the aluminum on which the anodized aluminum layer had been deposited was connected to the positive terminal of the power supply. The ion stream from the corona wire was image-wise modulated by means of a silk-screen emulsion of a resolution target bonded to the downstream side of the screen.

The latent image which resulted was toned by hand using a magnetic brush and the resulting image was found to have excellent resolution with very little background.

EXAMPLE 2 The procedure of Example 1 was repeated using an electrolytic bath of the following composition:

Borie Acid 70 grams Ethylene Glycol 500 grams Deionized Water 500 milliliters Ammonium Hydroxide (to adjust bath to pH 7.2)

The results obtained using this bath were comparable to those observed in Example 1.

EXAMPLE 3 A drum provided with the anodized aluminum surface produced by means of the electrolytic oxidation described in Example 1 was substituted for the imaging drum in a commercial elcctrophotographic copier. the

Addressograph-Multigraph Model 5000. and was found to successfully transfer and fix a commercially available pressure fusible toner to plain paper.

Although specific embodiments of the instant invention have been described for the purpose of illustration. it should be readily apparent that other embodiments may be devised using the system described in the foregoing description.

I claim: 1. A process for electrophotographic reproduction which comprises imparting a uniform electrostatic charge to a photoconductivc ion modulator,

exposing the charged ion modulator to a pattern of light and shadow corresponding to an original image which is to be reproduced, thereby producing a latent electrostatic image thereon.

passing ions through the ion modulator carrying said latent electrostatic image to selectively impinge upon a barrier type aluminum oxide on aluminum surface, whereby producing a latent electrostatic image thereon,

developing said latent electrostatic image with toner particles to produce a toned image thereon, transferring said toned image to a receiving material and fixing said toned image upon said receiving material.

2. A process according to claim 1 wherein said transferring and fixing are accomplished simultaneously.

3. A process according to claim 1 wherein said barrier type aluminum oxide is present as a layer about from 5,000 angstroms to 10.000 angstroms thick.

4. A process according to claim 1 wherein said receiving material is plain paper.

5. A process according to claim I wherein multiple copies are produced by repeating the developing, transferring and fixing steps without re-exposing said photoconductive ion modulator or reproducing the latent electrostatic image upon said surface between successive copies.

6. An electrophotographic reproduction machine which comprises a photoconductive ion modulator.

means for imparting a uniform electrostatic charge to said modulator. means for exposing said modulator to a pattern of light and shadow corresponding to an original image to be reproduced. thereby selectively discharging said modulator and producing a latent electrostatic image thereon. means for causing an ion stream to impinge upon said modulator carrying said latent electrostatic image.

dielectric means to receive ionspassed through said modulator in a pattern corresponding to said latent electrostatic image. means for developing the resulting latent electrostatic image upon said dielectric means. and

means for simultaneously transferring the resulting developed image from said dielectric means to a receiving material and fixing said image thereon without destroying the latent electrostatic image upon said dielectric means.

7. A machine according to claim 6 wherein said dielectric means is a barrier type aluminum oxide.

8. A machine according to claim 7 wherein the thickness of the barrier type aluminum oxide is about from 5.000 angstroms to 10,000 angstroms.

9. A machine according to claim 6 wherein said modulator is an ion modulator screen.

10. A machine according to claim 6 wherein said modulator is a conductive screen coated with a photoconductor.

11. A process according to claim 1 wherein said barrier type aluminum oxide is produced by oxidation of aluminum in a buffered acidic electrolytic bath of about pH 6 to pH 9 at a potential of about from volts to 700 volts for about from 30 minutes to 2 hours.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,907,560

DATED 1 Sept. 23, 1975 INVENTORQ) 2 Harvey J. Sable It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

TITLE PAGE, [54], delete "AND DIELECTRIC" second occurrence;

COL. 1, line 3, after "DIELECTRIC" delete "AND DIELECTRIC"; COL. 4, line 11, change "supplied" to applied COL. 7, line 22, change "whereby" to thereby Signed and Scaled this seventeenth Day Of February 1976 [SEAL] A ttes t:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner of Patents and Trademarks UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,907,560

DATED 1 Sept. 23, 1975 INV ENTOR($') I Harvey J. Sable it is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

TITIE PAGE, [54], delete "AND DIELECTRIC" second occurrence; COL. 1, line 3, after "DIELECTRIC" delete "AND DIELECTRIC"; COL. 4, line 11, change "supplied" to applied COL. 7, line 22, change "whereby" to thereby Signed and Sealed this seventeenth D 3) 0f February 1 976 [SEAL] Attest:

RUTH C. MASON C. MARSHALL DANN Arresting Officer Commissioner uflarenrs and Trademarks 

1. A PROCESS FOR ELECTROPHOTOGRAPHIC REPRODUCTION WHICH COMPRISES IMPARTING A UNIFORM ELECTROSTATIC CHARGE TO A PHOTOCONDUCTIVE ION MODULATOR, EXPOSING THE CHARGED ION MODULATOR TO A PATTERN OF LIGHT AND SHADOW CORRESPONDING TO AN ORIGINAL IMAGE WHICH IS TO BE REPRODUCED, THEREBY PRODUCING A LATENT ELECTROSTATIC IMAGE THEREON, PASSING IONS THROUGH THE ION MODULATOR CARRYING SAID LATENT ELECTROSTATIC IMAGE TO SELECTIVELY IMPINGE UPON A BARRIER TYPE ALUMINUM OXIDE ON ALUMINUM SURFACE, WHEREBY PRODUCING A LATENT ELECTROSTATIC IMAGE THEREON, DEVELOPING SAID LATENT ELECTROSTATIC IMAGE WITH TONER PARTICLES TO PRODUCE A TONED IMAGE THEREON, TRANSFERRING SAID TONED IMAGE TO A RECEIVING MATERIAL AND FIXING SAID TONED IMAGE UPON SAID RECEIVING MATERIAL.
 2. A process according to claim 1 wherein said transferring and fixing are accomplished simultaneously.
 3. A process according to claim 1 wherein said barrier type aluminum oxide is present as a layer about from 5,000 angstroms to 10,000 angstroms thick.
 4. A process according to claim 1 wherein said receiving material is plain paper.
 5. A process according to claim 1 wherein multiple copies are produced by repeating the developing, transferring and fixing steps without re-exposing said photoconductive ion modulator or reproducing the latent electrostatic image upon said surface between successive copies.
 6. An electrophotographic reproduction machine which comprises a photoconductive ion modulator, means for imparting a uniform electrostatic charge to said modulator, means for exposing said modulator to a pattern of light and shadow corresponding to an original image to be reproduced, thereby selectively discharging said modulator and producing a latent electrostatic image thereon, means for causing an ion stream to impinge upon said modulator carrying said latent electrostatic image, dielectric means to receive ions passed through said modulator in a pattern corresponding to said latent electrostatic image, means for developing the resulting latent electrostatic image upon said dielectric means, and means for simultaneously transferring the resulting developed image from said dielectric means to a receiving material and fixing said image thereon without destroying the latent electrostatic image upon said dielectric means.
 7. A machine according to claim 6 wherein said dielectric means is a barrier type aluminum oxide.
 8. A machine according to claim 7 wherein the thickness of the barrier type aluminum oxide is about from 5,000 angstroms to 10, 000 angstroms.
 9. A machine according to claim 6 wherein said modulator is an ion modulator screen.
 10. A machine according to claim 6 wherein said modulator is a conductive screen coated with a photoconductor.
 11. A process according to claim 1 wherein said barrier type aluminum oxide is produced by oxidation of aluminum in a buffered acidic electrolytic bath of about pH 6 to pH 9 at a potential of about from 100 volts to 700 volts for about from 30 minutes to 2 hours. 